The Sensitive Gut

Understanding IBS

Diarrhoea and constipation: chaos, control and a possible explanation.

irritable-bowel-syndrome-diarrhoea_and_constipation_1One of the most intriguing questions about IBS is why some people have diarrhoea most of the time, others have constipation and others seem to alternate between those two opposing physiological states. Does the same dichotomy exist in other aspects of physiology or behaviour? If we could get a handle on that, then we might be able to gain an crucial insight into what we call IBS but also other disorders of body regulation.

Over the years, I have been struck by how diarrhoea and constipation seemed to represent different states of being, which I have tended to characterise as ‘chaos and control’.

People with diarrhoea appear more anxious and out of control than those with constipation. They are also more likely to eat more and they often sleep badly.    Physiological measurements reveal that they have more rapid bowel transit and are more likely to have increased bowel sensitivity. My colleague, Dr Peter Whorwell has also told me that people with diarrhoea respond better to hypnotherapy.

People with constipation, on the other hand, are more withdrawn, depressed and ‘up-tight’. Many are on diets and some have anorexia, prompting me to think of those more severely affected as ‘nothing in, nothing out people’.

I realise these statements are impressions based on observation and experience; they will not apply to everyone, but they might offer a hypothetical framework for further investigation.


Before I left Sheffield University, I tried to organise a project to compare measures of emotional expressiveness in people with constipation and diarrhoea. My hypothesis was that people with diarrhoea would be more emotionally expressive and anxious and whereas those with constipation, would be emotionally shut down. This project was never completed. I could not convince my research students of the validity of this exercise and the project was abandoned. Nevertheless the question has always puzzled me.

In subsequent years, several clinical investigators have investigated the same problem from several different perspectives. Although ingestion of fructose, lactose and some other high FODMAP foods can result in soft or liquid stools in people with sensitive guts, there are times when they can ingest FODMAPs with impunity. Similarly high fibre diets are often ineffective in patients with constipation. The gut tends to be more permeable and the gut immune system more reactive in people with persistent diarrhoea following attacks of gastroenteritis, but that does not characterise everybody with diarrhoea and it is not necessarily absent in people with constipation.

The function of the autonomic nervous system has been measured in a few studies. These have demonstrated that heart rate variability is reduced both in patients with diarrhoea and those with constipation, indicating that the output from the ventral vagal complex is lower than normal. In other words the vagal brake on the alarm or collapse systems is reduced. There are also suggestions that people with constipation have higher sympathetic tone, alongside higher secretion of cortisol, which supplies the energy for mobilisation and one study claimed to show that vagal tone was increased after a meal in people with diarrhoea. These studies are difficult to interpret because the standard method of measuring vagal tone, heart rate variability only measures activity in the ventral vagal complex and not the dorsal vagal system that is associated with gut responses to trauma and stress. The only relevant index of dorso-vagal activity is intestinal transit, which has been associated with bowel habit for many years and could be due to changes in diet and absorption/secretion.

Alternating diarrhoea and constipation

Since diarrhoea and constipation might encompass many different disturbances in bowel function, it might be more instructive to study people with alternating diarrhoea and constipation. During the course of psychotherapy, I have had the opportunity to record in detail the narratives of several people with alternating symptoms.

Tanya came to see me with a strange set of symptoms, including diarrhoea, headaches, flushing in the face and ‘red hands’. This was the story she told. ‘I am a good time girl. I like to go out and party, drink and eat too much and enjoy letting it all go and having fun. That’s when I get the diarrhoea,  headaches and red hands.  After a few days of riotous living, I get fed up with myself and resolve to get back in control.  So I stay in, I work, watch television, eat sensibly, get some sleep and become constipated.  But that’s no life and so a few days later, I arrange to go out and the cycle starts again’.  I asked about her parents.  ‘My father is a hedonist; he loves life.  It’s my mother who keeps everything in control.’  Tanya’s oscillating bowel habit might be related to her diet and particularly her alcohol ingestion, but it also seemed that she had a conflict of identity, which was represented by her oscillating bowel habit.

Gemma had a different story.  She was a musician and would get diarrhoea if she was rehearsing for a performance. If on the other hand, there was no concert to prepare for, there was no challenge, she would try to work but get bored, mildly depressed and constipated.

So could diarrhoea and constipation be associated with other alternating states of physiology and behaviour: anorexia and bulimia, mania and depression and even as one of my colleagues has suggested, fibromyalgia and chronic fatigue?  In his recent workshop on ‘The Polyvagal Theory’,  Stephen Porges explained how release of the ventral ‘vagal brake’, can disinhibit both the sympathetic system for alarm and escape  and the dorsovagal system for letting go and immobilisation. Sometimes, one system can give way to the other. For example, animals, who freeze or collapse when cornered by a predator, will shake themselves vigorously to mobilise the sympathetic nervous system when the danger has passed. So might Tanya and Gemma oscillate between control and chaos while their bowels respond with constipation and diarrhoea? That would seem to make sense, but their responses seemed to me the wrong way round.

Chaos implies mobilisation and activation of the sympathetic nervous system, yet we know from a century of physiological observations that the sympathetic nervous system latter arrests motor activity of the colon, slowing propulsion, tightening the anal sphincter and causing constipation.  In contrast, when gut is irritated by infection, toxins, food intolerance or anxiety, it reacts with vomiting and diarrhoea, which are associated with activation of the ‘dissociative’ dorsovagal system and the release of serotonin.

Constipation is often associated with depression and boredom, which might seem to resemble dissociation.  In support of that, women who have been abused and suffer from post traumatic stress disorder and withdrawal are more likely to suffer from constipation. Yet drugs that mimic activity in the parasympathetic nervous system cause diarrhoea while those that block it are constipating.

How can it all make sense?

How can this conundrum be explained? I perused the scientific literature without enlightenment. The results confirmed what is known about the effects of the sympathetic and parasympathetic nerves on bowel function. Vagal activity was reduced and sympathetic activity was increased in patients with constipation, whereas after a meal, the vagal response was increased in patients with diarrhoea.

I slept on it – always a good idea. In the middle of the night I realised that I was looking at it the wrong way.  Instead of thinking that the wiring of the autonomic nervous system was somehow inconsistent, perhaps the way I was trying to understand it was too skewed by the more extreme reactions after trauma.  As Stephen Porges had explained, if the ventral vagal system is engaged, then it can modulate the activity in the other two systems so that we do not see the classic fight/flight or collapse, but observe less extreme expressions instead.  So the withdrawal of constipation could be seen as being tense, and ‘up tight’; an expression of bowel arrest that diverts energy to heart, lungs and muscles for purposes of mobilisation. Diarrhoea, on the other hand, might be regarded as the body letting go.   When Tanya was a party animal, she relinquished control, let go of everything and got ‘off her head’ to escape and have a good time. If that continued, she might dissociate and collapse. Gemma threw herself into the challenge of her performance and lost contact with reality, but could become seriously ill and have to stop.

We may need to view the three branches of the autonomic nervous system as able to function together. Both the sympathetic arousal and dorsovagal expulsion are turned on during sexual orgasm, while the ventral vagal keeps the mind in gear and tolerates the potential dangers of intimacy and immobilisation. Vomiting, another expulsive function, is a crisis in the gut, mediated by the dorsovagal but also demonstrating sympathetic components, such as sweating and yawning. The same might apply to diarrhoea, which is often associated with vomiting in order to clear the gut. Some people have even reported being deeply shamed by defaecation during orgasm.

Perhaps this might contain the seeds of a hypothesis, but it would require good on-line measures of activity in the dorso-vagal system to prove it.



Aggarwal, A., Cutts, T. F., Abell, T. L., Cardoso, S., Familoni, B., Bremer, J., & Karas, J. (1994). Predominant symptoms in irritable bowel syndrome correlate with specific autonomic nervous system abnormalities. Gastroenterology, 106(4), 945-950.
Increased SNS and reduced VT associated with constipation. Diarrhoea more parasympathetic

Elsenbruch, S., & Orr, W. C. (2001). Diarrhea-and constipation-predominant IBS patients differ in postprandial autonomic and cortisol responses. The American journal of gastroenterology, 96(2), 460-466. Increased postprandial vagal response in IBS D, increased cortisol

Heitkemper, M., Jarrett, M., Cain, K. C., Burr, R., Levy, R. L., Feld, A., & Hertig, V. (2001). Autonomic nervous system function in women with irritable bowel syndrome.


2 comments on “Diarrhoea and constipation: chaos, control and a possible explanation.

  1. Ali Bryant
    June 13, 2018

    Hi – great article. I can relate to this, I am torn between getting out and about doing things and then not wanting to go anywhere at all! I will have constipation (i will go most days but it is small lumps and difficult to pass) , then I will have literally just one bout of diarrhoea – could this one bout just be my body “clearing me out”?!


    • nickwread
      June 13, 2018

      How interesting it is that our bowels are so often a metaphor for the way we are; your constipation seems to represent not getting out and doing things.


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